As the charged particle beam application device, a charged particle beam length measuring device, a charged particle beam inspection device and the like have been known. The charged particle beam length measuring device and charged particle beam inspection device are used for manufacturing processes of, for example, semiconductors or magnetic discs. In this case, in the charged particle beam length measuring device, a charged particle beam (hereinafter, referred to also as a primary beam), such as an electron beam or an ion beam, is radiated onto a sample, and by acquiring a signal of a secondary charged particle beam (hereinafter, referred to also as a secondary beam) of secondary electrons or the like generated in accordance with the shape or size of a pattern formed on the sample, the shape or dimension of the pattern is measured. Moreover, in the charged particle beam inspection device, based upon the signal of the acquired secondary beam, a check is executed as to whether or not any pattern defect is present. As a specific example of these charged particle beam length measuring device and charged particle beam inspection device, a scanning electron microscope (hereinafter, referred to as “SEM”) has been conventionally known.
In recent years, in a semiconductor on which the length measurements or inspections are executed by using the SEM, high miniaturization of the semiconductor device has been developed and the miniaturization is coming to the limitation. For this reason, in order to further achieve high integration of the semiconductor device, a three dimensional configuration of the device has been developed in place of the miniaturization thereof.
In the semiconductor device having the three dimensional configuration, in order to execute inspections and/or length measurements, it is necessary to acquire information in the height direction of a sample in addition to observations in the planar directions, that is, observations of the planar shape or the dimensions of the sample. By radiating a tilted primary beam onto a sample, as well as by acquiring a signal of the secondary beam generated by the radiation of the beam, it is possible to also obtain the information of the height direction in accordance with the three dimensional configuration.
As the configuration for radiating the tilted primary beam to the sample, it is proposed to mechanically tilt a sample base or a sample stage on which a sample is mounted relative to the primary beam. In the general-use SEM, the sample can be cut out as a small piece. Therefore, by mounting the cut-out small piece of the sample on the sample base, the sample base is mechanically tilted, so that a tilted primary beam relative to the sample is radiated onto the sample.
On the other hand, the inspection and/or length measuring operations in the manufacturing process of a semiconductor are executed in a line for manufacturing the semiconductor device. That is, the SEM to be used for inspection and length measuring operations of the semiconductor is used as a process managing tool of the in-line. As a nature referred to as the process managing tool, a wafer on which a large number of semiconductor devices are formed is used as the sample. Therefore, the sample stage for use in mounting the wafer serving as the sample has a physically large size. When such a large sample stage is mechanically tilted, the action distance from the objective lens to the sample in the SEM inevitably becomes long, with the result that the resolution is lowered. For this reason, it is desired to execute an observation in a beam tilt system in which a defector is installed on the SEM and the electron beam is tilted electrically by the deflector. Although this system is advantageous in the period of time required for the tilting process and the reproducibility, a problem is raised in that deflection chromatic aberration and deflection comma aberration are increased because the electron beam passes through the inside of the objective lens at a position greatly apart from the optical axis.
A technique for cancelling the deflection chromatic aberration is described in, for example, Japanese Patent Application Laid-Open No. 2001-15055 (Patent Document 1). In Patent Document 1, a technique for cancelling the deflection chromatic aberration by installing a Wien filter is disclosed. Moreover, Japanese Patent Application Laid-Open No. 2007-128893 (Patent Document 2) has a description in accordance with a chromatic aberration corrector in which a transmission optical part for use in crossing charged particle beams (beams) having different energies in the vicinity of a lens main surface is indicated.